Abstract
We investigated series arrays of closely spaced, planar long Josephson junctions for magnetic field transduction in Earth’s field, with a linear response and high dynamic range. The devices were fabricated from thin film high-temperature superconductor YBa2Cu3O7−δ (YBCO) thin films, using focused helium ion beam irradiation to create the Josephson barriers. Four series arrays, each consisting of several hundreds of long junctions, were fabricated and electrically tested. From fits of the current-voltage characteristics, we estimate the standard deviation in critical current to be around 25%. Voltage-magnetic field measurements exhibit a transfer function of 42 mV/mT and a linear response over a range of 303 μT at 71 K, resulting in a dynamic range of 124 dB.
Highlights
Josephson junction devices are a leading candidate for magnetic field sensing due to their unique capability to quantum mechanically transduce magnetic flux into voltage
To improve single junction sensitivity, we propose to utilize long Josephson junctions
Parallel arrays can dramatically increase sensitivity; interference effects between junctions in parallel result in a highly nonlinear voltage response to applied magnetic flux which would be undesirable for unlocked operation
Summary
Josephson junction devices are a leading candidate for magnetic field sensing due to their unique capability to quantum mechanically transduce magnetic flux into voltage. Sensitivity, defined by the device transfer function, may be maintained through increasing the sensor voltage response by connecting very large numbers of SQUIDs together in series with the detriment to increased noise and strict junction uniformity requirements.
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